The present invention relates to electrical connectors and more particularly to air or fluid pressure actuated connectors for electrically connecting printed circuit boards or electrical parts.
During the post-manufacture of semiconductor devices and printed circuit boards, the components (whether they be individual integrated circuit devices or circuit boards containing integrated circuit devices) are subjected to test prior to their shipment. Electrical connectors for interconnecting components and circuit boards to testers and drivers are widely available. Typically, such connectors possess contacting elements that extend from the connector to effect contact with respective contact pads (e.g., gold plated pads) located on an external surface of the DUT. Contact is usually achieved through the use of some compression or clamping means that engages the contact elements with their respective contact pads. Zero insertion force (ZIF) card edge connectors are used to overcome those problems associated with high insertion forces, for example, see U.S. Pat. No. 3,795,888.
One type of zero insertion force connector utilizes fluid pressure to actuate an expandable bladder located within a housing of the connector to exert a force against a flexible circuit, see U.S. Pat. No. 5,071,357.
Some of this type of connector use a flexible circuit board which has, for example, both ends fixed, such as in U.S. Pat. No. 5,222,668, or, one end secured and free end fixed rotatable about moving fulcrum, such as in U.S. Pat. No. 5,813,876.
Although the use of pressure actuated zero insertion force connectors are known in the art, there are several problems that have yet to be overcome by current zero insertion force connector designs.
Thus, in the known art, there requires to be substantial structures extending beyond the contacts of the flexible circuit and these interfere with components or structures on the DUT. U.S. Pat. No. 5,813,876 is typical of this type of problem.
Another problem of connectors in the known art is the poor path control for the connector material, with deleterious effects on signal integrity, particularly crosstalk and impedance control.
Another problem common to connectors in the known art is that DUT may be damaged and have metal or fiberglass fragments protruding from its surface. In existing connectors this can severely damage the contact.
A further problem of existing connectors is that most have a large scrubbing distance. The life of the socket is directly proportional to the scrubbing distance, so the socket will have a shorter life than in a design with a very low scrubbing distance such as the present invention.
Also, in both cases, with fixed end and pivoting end connectors, significant pressure shall be applied to the flexible circuit to effect the connection, otherwise relatively thin circuits with high flexibility shall be used. However, to connect high speed devices, for example, DDR memory modules, 5 layer circuit is typically necessary. This means that the flexible circuit may require substantial force to deform that is close to its breaking point.
A final and critical problem of sockets with expanding bladders such as in U.S. Pat. No. 5,813,876, is that the expandable area is not fully constrained, allowing the bladder to expand to a size where the wall thickness is reduced to beyond its limit of elasticity. Where the wall is reduced to less than 50% of its static thickness, bladder failure can ensue.
The present invention overcomes or at least alleviates the problems mentioned above.
The present invention is an electrical connector for establishing an electrical connection between a printed circuit board device under test (DUT) and an electrical device, such as driving the DUT.
The connector includes a flexible circuit that is capable of both mating to a tester, or driver, and connecting electrically to the DUT.
The flexible circuit has a first surface and an opposite second surface and includes at least one metal layer and a plurality of electrically conductive contacts that are attached to the metal layer along the first surface. The flexible circuit has a portion secured to the contacts of the tester and opposite free second portion or portions that is used to make electrical contact to the DUT contact pads. A resilient bladder is positioned adjacent the free edge of the flexible circuit on its second surface opposite to first surface where contacts to the DUT are located and is capable of exerting a force against this first surface of the flexible circuit to cause the contacts on its second surface to physically engage contact pads of the printed circuit board under test. The flexible circuit is shaped by means of one or more formers. Once inserted, the DUT is secured by a lock so as to prevent voluntary removal and damage of the DUT.
A gas cylinder, pump, air compressor or other fluid pressure source is operatively coupled to the bladder for causing the bladder to exert a uniform force to the contacts of the flexible circuit to engage with the contact pads of the printed circuit board.
A piston and a buffer material, or a spring may provide an action equivalent to the bladder.